Excitation circuit for flectric valve apparatus



Feb. 2, 19.43. H, w LORD EXCITATION CIRCUIT FOR ELECTRIC VALVE APPARATUS Filed March 25, 1942 REACTOR VOLTAGE LOAD VOLTAGE Inventor Harold W Lord,

b His Attorney.

Patented Feb. 2, 1943 sxormrlon CIRCUIT Fon ELECTRIC VALVE arrm'ros Harold W. Lord, Schenectady, N. Y., assignor to General Electric Company, a corporation or New York Application March 25, 1942, Serial-No. 436,149 8 Claims. (01. 175-363) as the voltage or current of an associated circuit For example, in electric valve systems employing apparatus such as electric valves using ionizvalve means for producing a voltage to assist the control member voltage derived from the anodecathode circuit. In other embodiments of my invention, excitation means is provided for starting the electric valve means and after the system is initiated in its operation the control voltage for energizing the control member is derived exclusively from the reactor which is connected in I series with the anode-cathode circuit of the able mediums such as gases or'vapors, it is important to effect energization of the control member at a desired time during a cycle of voltage of alternating current so that the arc discharge is initiated at a precise instant. In accordance with the teachings of my invention described hereinafter, I provide new and improved control circuits whereby the precision of control is obtained without involving the use of expensive and elaborate associated control equipment.

It is an object of my invention to provide new and improved electric valve translating apparatus.

It is another object of my invention to provide new and improved control and excitation circuits for electric valve means employing control members which control the conductivity or control the amount of current conducted thereby.

It is a further object of my invention to provide new and improved control and excitation circuits for electric valve means of the type using immersion-ignitor control members.

Briefly stated, in the illustrated embodiments of my invention I provide new and improved control circuits wherein positive control and ignition of electric valve apparatus isaiiorded. The electric valve means is of the type comprising an ionizable medium, such as a gas or a vapor, and may include a control member of the immersion-ignitor type associated with the cathode and which when properly energized establishes an arc discharge between the anode and cathode. In one embodiment of my invention, an excitation circuit responsive to the anode voltage of the associated electric valve is employed to supply an impulse of current to the control member when the anode voltage is of a predetermined or positive polarity and when it attains a predetermined magnitude. In order to assure positive ignition of the electric valve means, I provide inductive means or a reactor which is connected in circuit with the anode-cathode circuit of the electric electric valve means.

For a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawing, and its scope is pointed out in the appended claims. Fig. 1 diagrammatically illustrates an embodiment of my invention as applied to a biphase rectifier, and Fig. 2 represents certain operating characteristics thereof. Fig. 3 represents a modification of the arrangement shown in Fig. 1 wherein an auxiliary source of excitation current is employed for initiating operation of the system.

Referring now to Fig. 1 of the drawing, I have there illustrated my invention as applied to an electric valve translating system, such as an else- -tric valve converting system, for energizing a direct current load circuit Lwhich may-be of the inductive type comprising an inductive reaetance 2 and a resistance 3, from an alternating current supply circuit E. The translating apparatus comprises an inductive network having a plurality of electrically displaced phase windings. The inductive network'may comprise a transformer 5 having a primary winding 6 and a pair of diametrically electrically displaced phase windings 'i and 8 which are respectively associated with electric valve means 9 and iii. The arrangement illustrated constitutes a bi-phase rectiiier. It will, of course, be understood that my invention in' its b'roaderaspects may be applied to electric valve circuits of a greater number of phases if desired.

The electric valve means 9 and in are preferably of the type employing an ionizable medium, such as a gas or a vapor, which is capable of supporting an arc discharge, and each includes an anode ii, a cathode H. such as a mercury pool cathode, and each may comprise a control member E3 of the immersion-ignitor'type constructed of a materia1 such as boron carbide or silicon carbide and which has an electrical resistivity substantially large compared with that of the associated mercury of the cathode into which it extends. Arc discharges are established between associated anodes and the cathodes upon electric valves.

iting resistances l8 and I9, respectively.

In order to assure positive ignition of electric valve means 9 and III by adding another component of firing voltage to the control member voltages derived from the anode-cathode circuits of the electric valve means, I provide an inductive means or a reactor 20 having a primary or main winding 2! which is connected in series relation with the electric valve circuits of electric valve means 9 and Ill, and which is also provided with a pair of secondary windings 22 and 23 which are connected in series relation with the rectifiers l6 and II, respectively. These windings are poled so that positive voltages are applied to the control members I3 in response to the voltage across the reactor 20 occasioned by the commutation of current between the electricvalve means 9 and Ill.

The operation of the embodiment of my invention shown in Fig. 1 will be explained by considering the system when it is operating as a bi-phase rectifier to transmit unidirectional cur rent and voltage to the load circuit I. The electric valve means 9 and I conduct current alternately during the positivehalf cycles of applied anode-cathode voltage, and the time when each electric valve means is rendered conducting during its positive half cycle of applied anodecathode voltage is determined by that time in the half cycle at which the anode-cathode voltage rises to a value sufliciently high to cause the transmission of a predetermined minimum critical current through the control member I3 and of transformer 5, and curves B and C represent the voltages provided by the secondary winding voltage goes negative and will persist during a period of time corresponding to the power factor angle or untilthe other electric valve means is rendered conducting If it be assumed that the electric valve means In and 9 are rendered conducting at times 0 and 11, respectively, and if the load circuit is inductive, it will be appreciated that the current through the electric valve means will continue throughout the respective negative regions a-c and bd.. Inasmuch as considerable inductance is present in the load circuit, the current supplied to the load circuit will remain substantially constant and thevoltage variation due to the sinusoidal variation of the positive or rectified voltages derived from windings I and 8 will be absorbed across the primary winding 2! of the reactor'20. For example, at the time of commutation of current from electric valve means 9 to electric valve means Hi, the difference in anode-cathode voltages represented by the quantity e is absorbed by the reactor 20. It is this variation of voltage which is utilized by the reactor 20 to produce voltages which assist the components of voltage derived from the respective anode-cathode circuits of electric valve means 9 and I0 and which are applied to the control members 03.

Curve D of Fig. 2 represents the voltage applied to the load circuit I. Curves E and F represent the positive or rectified half cycles of the alternating voltages furnished by secondary windv ings I and 8 of transformer 5. The difference between the voltages represented by curves E and F and the load voltage D is the ripple voltage which appears across the primary winding 2| of reactor 20 This difference voltage is represented by curve G and is the voltage which induces the additive or assisting voltages in windings 22 and 23.

Fig. 3 diagrammatically illustrates a modification of the arrangement shown in Fig. 1, and corresponding elements have been assigned like reference numerals. In this modification, the

vice 29, so that the time of application of energizing voltage to control members I3 is controllable. Relay 26 comprises an actuating coil 30 and may include pairs of contacts 31-34, inclusive. Relay 26 is arranged so that when in the d eenergized position the auxiliary source of excitation 21 is connected to control members l3 of electric valve means 9 and I0 through contacts 34 and 32, respectively. When relay 26 is in the closed or energized position, the auxiliary sourceof excitation 21 is disconnected and the secondary windings 22 and 23 of the reactor are connected to control members l3 of the electric valve means 9 and 10, through contacts 3| and 33 respectively. v

I also provide current responsive means for actuating the relay 2! in response to an electrical condition of the load circuit such as the current conducted by the electric valve means 9 and ID to disconnect the auxiliary source of excitation 21 from the control members l3 as soon as the current begins to flow in the anodecathode circuit or the load circuit. This current responsive means may comprise means such as a shunt 35 which supplies a voltage to the actuating coil 30 of relay 26 when current is transmitted to the load circuit l.

The embodiment of my invention illustrated in Fig. 3 operates in substantially the same way as that explained above in connection with the arrangement in Fig. 1. During the initiating operation of the system, impulses of positive unidirectional current are transmitted to the control members l3 of electric valve means 9 and I in timed relation to render the electric valve means 9 and I0 conducting alternately As soon as current is transmitted to load circuit I, relay 26 is energized, thereby disconnecting the auxiliary source of excitation 21 from the control members l3, and connecting secondary windings 22 and 23 to the control members l3 through rectifiers 24 and 25. The variation in voltage appearing across the reactor 2l,--as. ex-

plained above in connection with the operation of Figs. 1 and 2, is utilized to produce voltages which are sufficient to render the electric valve means 9 and I0 conducting at the desired times.

It will be appreciated that the magnitude of the voltage which is supplied to control members 13 in the arrangements shown in Figs. 1 and 3 may be controlled, adjusted, or determined by the design of the reactor with particular regard to the ratio of turns of the primary winding 2! and the secondary windings 22 and 23.

While I'have shown and described my invention as applied to particular systems of connections and as embodying various devices diagrammatically shown, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of. the United States is:

1. In combination, an alternating current circuit, a load circuit, bi-phase electric valve translating apparatus connected between said circuits and comprising a pair of windings displaced 180 electrical degrees relative to the voltage of said alternating current circuit and including a pair of electric valve means each associated with a different one of the windings, said electric valve means each being of the type comprising an anode, a cathode and a control member of the immersion-ignitor type associated with said cathode, and an inductive device connected in series relation with the anode-cathode circuits of both of said electric valve means and said load circuit and comprising a pair of secondary windings respectively connected to the control members of the pair of electric valve means for producing volta es to energize said control members.

2. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising an inductive network including a plurality of electrically displaced windings and a plurality of electric valve means each associated with a different one of the windings, said electric valve means being of the type comprising an anode. a cathode and a control member, an inductive device connected in series relation with the anodecathode circuits of said electric valve means and said load circuit, means responsive to the variation in voltage. across said inductive device for members, an auxiliary source of excitation current for energizing said control members, and

, producing a voltage to energize said control necting said auxiliary source to said control members.

3. In combination, 'an alternating current circuit, a load circuit, electric translating apparatus connected betweensaid circuits and comprising an inductive network including a plurality of electrically displaced windings and a plurality of electric valve means each associated with a different one of the windings, said electric valve means being of the type comprising an anode, a cathode and a control member, an inductive device connected in series relation with the anode-cathode circuits of said electric valve means and said load circuit, means responsive to the variation in voltage across said inductive device for producinga voltage to energize said control members, an auxiliary source of excitation current for energizing said ntrol members, and means responsive to the fio, 01 current in the anode-cathode circuits of said electric valve means for selectively disconnecting and connecting said auxiliary source to said control members.

4. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising an inductive network including a plurality of electrically displaced windings and a plurality of electric valve means each associated with a different one of the windings, said electric valve means being of the type comprising an anode, a cathode and a control member, an inductive device connected in series relation with the anodecathode circuits of said electric valve means and saidload circuit, means responsive to the variation in voltage across said inductive device for producing a voltage to energize said control members, an auxiliary source of excitation current for energizing said control members, and means for selectively connecting said auxiliary source and said last mentioned means to said control members in response to the current transmitted to said load circuit.

5. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising an inductive network including a plurality of electrically displaced windings and a plurality of electric valve means each associated with a different one of the windings, said electric valve means being of the type comprising an anode, a cathode and a control member, an in ductive device connected in series relation with the anode-cathode circuits of said electric valve means and said load circuit, means responsive to the variation in voltage across said inductive device for producing a voltage to energize said control members, an auxiliary source of excitation current for energizing said control members, and means for selectively connecting said auxiliary source or said last mentioned means to said control members in response to an electrical condition of said load, circuit.

6. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising an inductive network including a plurality of electrically displaced windings and a plurality of electric valve means each associated with a different one of the windings, said electric valve means being of the type comprising an anode, a cathode, an immersion-ignltor type control member associated with said cathode and employing an ionizable medium capable of supporting an arc discharge, a plurality of means each assoanode, and means responsive to the current conducted by said electric valve means and utilizing the voltage during the commutation of current from one electric valve means to another for adding a voltage to the control member voltage derived from the anode-cathode circuit thereby assuring positive ignition of the electric valve means.

'7. In combination, an alternating current circuit, a, direct current circuit, electric translating apparatus connected between said circuits and comprisinga plurality of electrically displaced phase windings and a plurality of electric valve means each connected to a difierent one of said phase windings, saidelectric valve means each comprising an anode, a cathode, an immersionignitor type control member in contact with said cathode and employing an ionizable medium capable of supporting an arc discharge, a plurality of means each associated with a difierent one of said electric valve means and each connected between the anode and thecontrol member for transmitting thereto unidirectional current for initiating an arc discharge'within the electric valve means, and means connected in the direct current circuit and responsive to the voltage thereacross occasioned by the commutation of current among the electric valve means for producing a voltage to assist the control member voltage derived from the anode-cathode circuit of the various electric valve means thereby assuring positive ignition of the electric valve means.

8. In combination, an alternating current circuit, a direct current circuit, electric translating apparatus connected between said circuits and comprising a pair of diametrically displaced phase windings and a pair of electric valve means each connected to a difierent one of said phase windings, said electric valve means being of the type comprising an anode, a cathode, an immersion-ignitor type control member associated with said cathode and employing an ionizable medium capable of supporting an are discharge, a pair of rectifiers each connected in circuit with'the anode of a difierent one of said electric valve means and poled to transmit posi tive current to the associated control member,

and comprising an inductive device having a main winding connected in circuit with said direct current circuit and having a pair of poled secondary windings each connected in series relation with the control member and associated rectifier of the electric valve means.

HAROLD W. LORD. 

